Poly(sialate-disiloxo)-based geopolymeric cement and production method thereof

ABSTRACT

The invention relates to a geopolymeric cement or binder comprising an amorphous vitreous matrix consisting of a poly(sialate-disiloxo)-type geopolymeric compound, having approximation formula (Na, K, Ca)(—Si—O—Al—O—Si—O—Si—O) or (Na, K, Ca)-PSDS. The inventive cement consists of a mixture of different varieties of polysialates in which the atomic ratio Si:Al varies between 2 and 5.5, the average of the Si:Al atomic ratio values as measured with the electronic microprobe being close to between 2.8 and 3. The remaining components of the geopolymeric cement or binder, such as mellilite particles, aluminosilicate particles and quartz particles, are not used in said Si:Al atomic ratio calculation. The geopolymeric structure of type (K, Ca)-Poly(sialate-disiloxo) (K, Ca)-PSDS is between 50% and 60% more mechanically resistant than that of type (K, Ca)-Poly(sialate-siloxo) (K, Ca)—PSS of the prior art.

The present invention relates to a new type of geopolymeric cementintended for construction. This cement is called geopolymeric cementbecause it contains geopolymer minerals, consisting of alkalinealuminosilicates, best known under the name of poly(sialate),poly(sialate-siloxo) and/or poly(sialate-disiloxo). In the case of thisinvention, the geopolymeric cement is based on poly(sialate-disiloxo).

Former Techniques.

Two different types of cement may be distinguished: hydraulic cementsand geopolymeric cements. Geopolymeric cements result from a mineralpolycondensation reaction by alkaline activation, known as geosynthesis,in opposition to hydraulic traditional binders in which hardening is theresult of a hydration of calcium aluminates and calcium silicates.

The poly(sialate) term was adopted to indicate the aluminosilicatesgeopolymers. The sialate network consists of SiO₄ and AlO₄ tetrahedronsalternatively bound by oxygen atoms. Cations (Na+, K+, Ca++, H₃O+)present in the structural cavities of the poly(sialate) balance thenegative charge of Al³⁺ in coordination (IV). The empirical formula ofPolysialates is: Mn{—(SiO₂)z-AlO₂}n, wH₂O, with M representing thecation K, Na or Ca and “n” the degree of polymerization; “z” is equal to1, 2, 3 or more, until 32. The three-dimensional network (3D)geopolymers are of type:

Poly(sialate) M-PS Si:Al = 1:1 Mn—(—Si—O—Al—O—)n Poly(sialate-siloxo)M-PSS Si:Al = 2:1 Mn—(Si—O—Al—O—Si—O—)n Poly(sialate-disiloxo) M-PSDSSi:Al = 3:1 Mn—(Si—O—Al—O—Si—O—Si—O—)n

The geopolymeric binders or cements of the types poly(sialate),poly(sialate-siloxo) and/or poly(sialate-disiloxo), were the subject ofseveral patents highlighting their particular properties. One can quotefor example the French patents: FR 2.489.290, 2.489.291, 2.528.818,2.621.260, 2.659.319, 2.669.918, 2.758.323.

Geopolymeric cements of the prior art (WO 92/04298, WO 92/04299, WO95/13995, WO 98/31644) are the result of a polycondensation betweenthree distinct mineral reagents, i.e.:

-   a) aluminosilicate oxide (Si₂O₅, Al₂O₂)-   b) potassium or sodium disilicate (Na, K)₂(H₃SiO₄)₂.-   c) calcium disilicate Ca(H₃SiO₄)₂

With potassium disilicate, polycondensation is the result of thefollowing chemical reaction:2(Si₂O₅, Al₂O₂)+(Na, K)₂(H₃SiO₄)₂+Ca(H₃SiO₄)₂→(K₂O, CaO)(8SiO₂, 2Al₂O₃,nH₂O)  (1)

The obtained geopolymer is of the type (K, Ca)-Poly(sialate-siloxo), (K,Ca)-PSS with Si:Al=2. Then one adds various reactive mineral fillerslike silica (silica fume), or natural aluminosilicates.

The reagents a) and b) are industrial reactive products added in thereactive medium. On the other hand, the ingredient c), calciumdisilicate, occurs in a naissant state, in situ, in strong alkalinemedium. It results in general from the chemical reaction between calciumsilicate such as calcium mellilite present in blast furnace slag.

One of the interesting properties of geopolymeric cements is that duringtheir manufacture they release very little of the greenhouse gas, carbondioxide CO₂, whereas cements containing Portland cement clinker emit agreat deal of carbon dioxide. As one can read in the publicationentitled Global Warming Impact on the Cement and Aggregates Industries,published in World Resource Review, Vol. 6, NR 2, pp 263-278, 1994, oneton of Portland cement releases 1 ton of gas CO₂, whereas geopolymericcement releases 5 to 10 times less. In other words, within the frameworkof the international laws and protocols limiting future CO₂ emissions, acement manufacturer initially producing Portland cement will be able toproduce 5 to 10 times more geopolymeric cement, while emitting the samequantity of CO₂. The appeal of geopolymeric cements is very obvious forthe economies of the developing countries.

Thus, the French patent FR 2.666.253 describes a process for obtaininggeopolymeric cement, without carbon dioxide CO₂ emission, in which thematrix, after hardening, is a geopolymer of the type (Ca, Na,K)-poly(sialate-siloxo), (Ca, Na, K)-PSS, in which the atomic ratioSi:Al is equal to 2. In the present invention, the matrix is of the type(Ca, Na, K)-poly(sialate-disiloxo), (Ca, Na, K)-PSDS and the atomicratio Si:Al in the vitreous matrix is close to 3, this beingcharacteristic of a geopolymer different from that of the prior art.

However, one finds in the prior art a manufacturing process for ageopolymer of the type (Na, K)-poly(sialate-disiloxo), (Na, K)-PSDS. Asit is described in the European patent EP 0 518 980, one exclusivelyuses an alkaline solution of a very special silica obtained in anelectric furnace, and the reactive mixture contains sodium Na, orpotassium, K, alkaline silicates, but does not include any calcium Ca.In the present invention one does not use this artificial thermalsilica, but only aluminosilicate materials of geological origin, moreprecisely residual rocks with strongly advanced kaolinization.

In another patent of the prior art, publication WO 92/04299 of thePCT/CH91/00187, was mentioned a cement that containstecto-alumino-silicates resulting from the reaction between metakaolin,reactive silica, aluminosilicate chemically activated at a temperaturebetween 800° C. and 1200° C., soluble alkali silicate, alkali hydroxide(KOH or NaOH), and calcium silicate. One obtains an aluminosilicatecement whose general formula gives an atomic ratio Al:Si in the range of4:6 to 4:14, that is to say a Si:Al ratio varying from 1.5 to 3.5.However, it is specified that it is a general formula, including the sumof all the components, namely the soluble compounds that make thematrix, to which are added the insoluble elements still in the form ofgrains and particles. In fact, in this cement of the prior art, theactive matrix (called here in the present invention vitreous matrix) isof the type (Ca, Na, K)-poly(sialate-siloxo), (Ca, Na, K)-PSS, likeother geopolymeric cements of the prior art. The proof is provided byFIG. 7 of the publication WO 92/04299, which reproduces the NuclearMagnetic resonance spectrum of 29Si. This 29Si spectrum consists of tworesonances, one at −94.5 ppm, the other at −113.9 ppm, and is similar tothat of geopolymeric cement described on pages 113 to 117 of thescientific publication titled: Geopolymers: Man-Made Rock Geosynthesisand the resulting development of very early high strength cement,published in Journal of Material Education, Vol. 16, pp. 91-137, 1994(see also on pages 136-138 of the publication entitled: Properties ofGeopolymer Cements, published in Proceedings of the International FirstConference on Alkaline Cements and Concretes, Kiev, 1994). The firstresonance at −94.5 ppm corresponds to a SiQ₄(2Al) site, i.e. preciselythe structure for poly(sialate-siloxo) PSS, with Si:Al=2. The secondresonance at −113.9, is that of SiO₂, SiQ₄(0Al), i.e. either ofinsoluble quartz or silica particle. It is therefore proven that thegeneral chemical formula disclosed in publication WO 92/04299, in whichthe Si:Al ratio varies from 1.5 to 3.5, is the result of the addition ofall the elements, in particular of insoluble silica. It is not thechemical formula of the vitreous matrix, which has a Si:Al ratio closeto 2. On the contrary, in the present invention, the chemical formula ofthe vitreous matrix does not take into account the particles and grainswhich are embedded in it. In the matrix of this invention, theaforementioned geopolymer compound of the Poly(sialate-disiloxo) typeconsists of a mixture of different varieties of polysialates in whichthe atomic ratio Si:Al varies between 2 and 5.5, the average of thevalues of the atomic ratio Si:Al being close to 2.8 to 3. The othercomponents of the aforesaid binding or geopolymeric cement, such as theparticles of mellilite, the aluminosilicate particles, the quartzparticles, or the silica particles, do not enter into the calculation ofthis atomic ratio Si:Al.

Another example of geopolymeric cement of the prior art is described inthe publication WO 98/31644 for PCT/FR98/00059. In this description, thegeopolymeric vitreous matrix is characterized by its 29Si MAS-NMRspectrum. Thus, one can read on page 9, lines 1-7 that the spectrum hasa resonance ranging between −85 and −89 ppm characteristic of a mixtureconsisting of (SiO₄) sites of the type SiQ₄(3Al, 1Si) associated with ahydroxylated aluminosilicate (SiO₄) of the type Q₃(2Si, 1Al, 1OH). Oneobtains a geopolymeric compound made of a poly(sialate), Si:Al=1 mixedwith a poly(sialate-siloxo), Si:Al=2, the aforementioned compound havinga Si═Al ratio close to 1.6. Such a matrix is described hereafter inExample 1.

All geopolymeric cements of the prior art are characterized by theextremely fine grain size of the principal solid components. The averagegrain size is about 8 microns (WO 98/31644, page 9 line 36 and page 10line 17), even as low as 3.5 microns (WO 92/04299, page 16 Beispiel 4).Indeed, in the prior art, the objective was to produce a cement withultra-fast setting, and for this reason it was necessary to ensure amaximum solubilization of the solid reagents; this explains the need forthe finest possible grain size. Thus, one can read in the publication WO92/04298, page 10, lines 10-16 and 38-40, that the basic silicates areafter 30 minutes transformed into soluble naissant calcium disilicate.On the other hand, in the present invention, the average diameter is inthe range between 15 microns and 25 microns, thus preventing anydissolution of the mellilite and natural silico-aluminates particles inthe aforementioned amorphous vitreous matrix. In the present invention,the hardening mechanism is different from the one in the prior art,because there is no formation of calcium disilicate, but primarilycation exchanges between the alkali cations (Na, K)+ and the CalciumCa++ cation.

BRIEF DESCRIPTION OF THE INVENTION

The principal object of the invention is the description of ageopolymeric binder or cement consisting of an amorphous vitreous matrixembedding mellilite particles, aluminosilicate particles and quartzparticles, said particles having an average diameter lower than 50microns. In the binder or cement of the present invention theaforementioned amorphous vitreous matrix comprises a geopolymer compoundof the Poly(sialate-disiloxo) type, with the approximate formula (Na, K,Ca)(—Si—O—Al—O—Si—O—Si—O), or (Na, K, Ca)-PSDS. The said geopolymercompound of the Poly(sialate-disiloxo) type consists of a mixture ofdifferent varieties of polysialates in which the atomic ratio Si:Alvaries between 2 and 5.5, the average of the values of the atomic ratioSi:Al being close to 2.8 to 3. The other components of the saidgeopolymeric binder or cement, such as the mellilite particles, thealuminosilicate particles and the quartz particles, do not enter intothe calculation of this atomic ratio Si:Al.

This new geopolymeric binder or cement is obtained by hardening areactive mixture comprising:

-   a) a residual rock from a strongly weathered granitic type in which    the kaolinization is far advanced;-   b) calcium mellilite glass in which the glass part is higher than    70% by weight;-   c) a soluble alkaline silicate in which the molar ratio (Na,    K)₂O:SiO₂ ranges between 0.5 and 0.8;

The aforementioned residual rock of weathered granitic type consists of20 to 80 percent by weight of kaolinite and 80 to 20 percent by weightof feldspathic and quartzitic residual sands. In order to increase thegeopolymeric properties of the binders or cements described in thisinvention, it is preferable that the aforementioned residual rock iscalcined at a temperature ranging between 650° C. and 950° C. Thisallows the use of a mining waste produced during the extraction of coal,in place of the residual rock of weathered granitic type,

In the preparation of the binders and cements according to the presentinvention, the average diameter of the grain size distribution for thecalcium mellilite glass lies between 15 microns and 25 microns, thuspreventing the dissolution of these particles of mellilite in theaforementioned amorphous vitreous matrix.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The scientific analysis of the geopolymeric binders or cements isperformed with the electron microscope micro-beam analysis. With thistechnique it is possible to determine unambiguously the chemicalcomposition of the three principal components comprising the cements ofthis invention, namely:

-   the amorphous vitreous matrix;-   the particles of the calcium mellilite glass;-   the aluminosilicates rock particles (feldspars, plagioclase,    feldspathoïd, zeolite, pyroxene, amphibole) and quartz.

The binders or cements of this invention are illustrated in thefollowing examples. They have no limiting character on the scope of theinvention as presented in the claims. All indicated parts are by weight.

EXAMPLE 1

In order to understand better the difference between the vitreous matrixof this invention and those of the prior art, this example replicatesthe cement known as “base” and described in the publication WO 98/31644,page 9, lines 30-39, i.e.:

calcined kaolinitic clay 30 parts aluminosilicate oxide (Si₂O₅, Al₂O₂) Ksilicate solution, 25 parts (by weight) K₂O: 26%, SiO₂: 21%, H₂O: 53%blast furnace slag (calcium mellilite) 27 parts average grain size 8microns water 31 parts

The objective of the prior art being to manufacture the calciumdisilicate Ca(H₃SiO₄)₂, in situ, the electron microscopy of the cementthus obtained must show the disappearance of the calcium melliliteparticles, as can be read in this same publication on page 7, lines13-20, namely: “. . . When, under the microscope, [S.E.M.], one looks atthe cements obtained with the mixtures described in the examples 1 to10, one notes that, in the case of blast furnace slag, the majority ofthe slag grains have disappeared. One only sees an imprint of theirinitial shape, in the shape of an envelope, probably made up ofakermanite, which did not react This process is very regular and can becomplete within 30 minutes, at ambient temperature.)

The chemical composition for this cement is given as oxides in Table I.The values for water were omitted voluntarily.

TABLE I SiO₂ Al₂O₃ Fe₂O₃ MgO CaO Na₂O K₂O (Si₂O₅, 16.33 12.76 0.15 0.0960.012 0.042 0.439 Al₂O₂) Ca 9.58 3.24 0.054 2.43 11.34 0.054 0.135mellilite K- 5.23 0 0 0 0 0 6.495 silicate. total 31.15 16.00 0.210 2.5211.35 0.096 7.069 oxides by weight total in 0.519 0.157 0.063 0.200.0015 0.0752 mole

The oxide mole values provide the atomic ratios:

Si:Al 1.65 K:Al 0.48 Si:K 3.43 Ca:Al 0.65 Si:Ca 2.53

After hardening, the electronic micro beam analysis provides the oxidechemical composition for the vitreous matrix in which the calciummellilite grains have practically all disappeared. Only some coarsegrains remain with a size higher than 20 microns. One makes 14 microbeam measurements on the vitreous matrix. The average value of thesemeasurements provides the following atomic ratios (between brackets, thelowest and the highest values):

Si:Al 1.655 (1.317 to 1.832) K:Al 0.442 (0.192 to 0.614) Si:K 3.73 Ca:Al0.679 (0.388 to 0.870) Si:Ca 2.43

Calcium mellilite effectively dissolved, resulting in the formation, insitu, of calcium disilicate Ca(H3SiO4)2. The obtained geopolymericcompound is thus made up of a simple mixture of poly(sialate) (K,Ca)—PS, Si:Al=1, and of poly(sialate-siloxo), (K, Ca)-PSS, Si:Al=2, theaforementioned compound having a Si═Al ratio close to 1.6, according tothe chemical reaction (1) described above.

EXAMPLE 2

One prepares a first mixture (A) made of aluminosilicate powderscomprising:

A) Mixture

aluminosilicate oxide (Si₂O₅, Al₂O₂) 30 parts feldspathic rock ground at15–25 microns 50 parts calcium mellilite ground at 15–25 microns 30parts

To these 110 parts of (A) mixture are added the reactive mixture (B)containing:

B) Mixture

the K silicate solution, 30 parts (by weight) K₂O: 26%, SiO₂: 21%, H₂O:53% water 15 parts

As it is noted, the average grain size of the feldspathic rock and ofthe calcium mellilite is higher, ranging between 15-25 microns, which isquite different from the prior art. In addition to the patents alreadyreferred to above, which all recommend average grain sizes lower than 10microns, one can also quote the Forss patents, which first recommendedthe use of alkaline activation for blast furnace slag, such as forexample the U.S. Pat. No. 4,306,912. In the Forss patents, the averagegrain size is expressed by its specific surface that is higher than 400m2/kg, preferably ranging between 500 and 800 m2/kg, i.e. below 10microns.

One lets this mixture harden at ambient temperature. The compressivestrength at 28 days is 70 MPa. Then, one looks at the compound with theelectron microscope. The obtained geopolymeric cement consists of threedistinct elements:

-   a) a vitreous matrix-   b) calcium mellilite particles-   c) feldspathic rock particles

The micro-beam analysis provides the chemical composition of these threeelements. The average value of these measurements provides the followingatomic ratios (between brackets, the lowest and the highest values):

-   a) vitreous matrix

Si:Al 2.854 (2.047 to 5.57)  K:Al 0.556 (0.306 to 0.756) Si:K 6.13(3.096 to 9.681) Ca:Al 0.286 (0.107 to 0.401) Si:Ca 15.02 (4.882 to41.267)

-   b) calcium mellilite particles

Table II gives the chemical composition of calcium mellilite, and theaverage of the 15 measurements provided by the electronic micro beam(values expressed by weight).

TABLE II Ca Mellilite Average micro beam K₂O 0.5 1.55 SiO₂ 35.5 35.38CaO 42 37.57 Na₂O 0.2 0.22 Al₂O₃ 12 11.93 MgO 9 8.59

-   c) feldspathic rock particles

Table III gives the chemical composition of the feldspathic rock and theaverage of the 15 measurements provided by the electronic micro beam forthe alkaline feldspar particles (values expressed by weight).

TABLE III feldspathic rock Average micro beam feldspar K₂O 4.89 7.55SiO₂ 74.16 66.05 CaO 0.43 0.38 Na₂O 4.33 6.20 Al₂O₃ 13.80 19.25 MgO 0.170.02

It is first noted that, in the vitreous matrix, the Si:Al ratio is muchhigher than that of Example 1) since the average value increases from1.65 to 2.85. There is thus an additional value for silica which canonly come from the siliceous part of the feldspathic rock, by which thecontent of SiO₂ decreases from 74,16 to 66,05 (see Table III). However,according to Table II, there is no difference between the chemicalanalysis of the Ca mellilite carried out before the mixture and theaverage value of the 15 micro beam measurements; SiO₂ quantity remainsequal to approximately 35.5. In other words, the silica found in thevitreous matrix of this Example 2) does not come from the calciummellilite, but exclusively from the feldspathic rock. Contrary to thecements of the prior art, there is no production of calcium disilicateCa(H₃SiO₄)₂

One then notes in Table II, that the quantity of K₂O in the calciummellilite particles is multiplied by 3, passing from 0.5 to 1.55, withvalues being able to reach 4.11, even 8.2 for certain particles. On theother hand, the quantity of CaO changed from 42 to 37.5. One nowunderstands why in the vitreous matrix of this Example 2), the quantityof potassium K is weaker than in the matrix of the Example 1). Part ofthe potassium present in the reactive medium happened to be fixed in theparticles of Ca mellilite, to replace the Calcium atoms which are nowincluded in the geopolymeric vitreous matrix. For calcium mellilite, thehardening at ambient temperature shows a reduction of 10 to 20% byweight of its content in CaO, simultaneously accompanied by an increaseof 100 to 500% (on average 300%) by weight of its content in K2O, thecontent of the other components like SiO₂, Al₂O₃ and MgO, beingunchanged. This exchange is a complete surprise, because nothing in theprior art could forecast this mechanism. It is supposed that it isprimarily due to the fact that the grain size of Ca mellilite beinghigher than in the prior art, the dissolution rate of silica pertainingto the feldspathic rock is much faster than that of the dissolution ofthe calcium disilicate. Only a small quantity of calcium has time toleave the mellilite particle, being immediately replaced by a certainquantity of potassium.

Another surprise comes from the fact that this mechanism ends with theformation of a geopolymeric cement having mechanical strengthssignificantly higher than those of the prior art. Thus, in publicationWO 98/31644,28 day compressive strengths are ranging between 30 and 60MPa, whereas in this Example 2) they are ranging between 80 and 100 MPa.The geopolymeric structure of type (K, Ca)-Poly(sialate-disiloxo) (K,Ca)-PSDS is thus 50% to 60% more resistant mechanically than that oftype (K, Ca)-Poly(sialate-siloxo) (K, Ca)-PSS of the prior art.

EXAMPLE 3

One takes the same reactive mixture of Example 2), but in the (A)mixture one adds 45 parts of calcium mellilite with an average grainsize of 15-25 microns, instead of 30 parts. The other conditions areunchanged. The 28 day compressive strength of the geopolymeric cement is120-130 MPa.

Instead of making a mixture of oxide aluminosilicate and feldspathicrock as in Example 2), one uses naturally occurring geological productscontaining these two elements. Indeed, the prior art teaches us that thealuminosilicate oxide (Si₂O₅, Al₂O₂) is obtained by calcining kaolinitebetween 650° C. and 950° C. This material, kaolinite, is the result ofthe weathering of feldspars and it is naturally found in weatheredgranitic residual rocks. The weathered granitic residual rock consistsof 20 to 80 percent by weight of kaolinite and 80 to 20 percent byweight of feldspathic and quartzitic residual sand containing reactivesilica.

In order to have a maximum reactivity, the weathered granitic residualrock in which kaolinization is very advanced, is calcined at atemperature ranging between 650° C. and 950° C. and, on the one handground at an average grain size of 15-25 microns for the feldspathic andquartzitic parts, the kaolinitic part, and on the other hand, havingnaturally a quite lower particle size.

EXAMPLE 4

One takes again the reactive mixture of Example 3) but instead ofcarrying out a mixture of aluminosilicate oxide and feldspathic rock,one adds 100 parts of a residual granite initially containing 35% ofkaolin by weight. This granite was calcined at 750° C. for 3 hours, thenground to an average grain size of 15-25 microns for the feldspathic andquartzitic parts. The other conditions are unchanged. The compressivestrength at 28 days for the geopolymeric cement is 125 MPa.

EXAMPLE 5

One chooses as residual rock, pertaining to the strongly weatheredgranitic type in which kaolinization is very advanced, the waste of coalmining. Throughout the world, coal veins are very often imprisonedbetween geological layers of kaolinitic granite. Sometimes, when coalwas naturally ignited, heat was sufficient to transform kaolinite intoaluminosilicate oxide (Si₂O₅, Al₂O₂). Such a natural layer exists inAustralia, but is not exploited. On the other hand one canadvantageously calcine kaolinitic coal-mining rock waste. The chemicalanalysis of a rock of this type is as follows:

coal 3.07 SiO₂ 63.71 Al₂O₃ 13.44 Fe₂O₃ + FeO 4.72 MgO 2.31 CaO 2.72 Na₂O1.88 K₂O 2.40 H₂O+ 3.20 H₂O− 1.34

It contains approximately 25% plagioclase (feldspar), 30% quartz, 10%amphibole, 27% kaolinite, 3% coal and 6% of other elements.

One calcines it at 750° C. for 3 hours, then one grinds it to an averagegrain size of 15-25 microns.

Then, one prepares the following reactive mixture:

a) kaolinitic coal-mining waste, 90 parts b) calcium mellilite ground to15–25 microns 30 parts c) K silicate solution, 30 parts (by weight) K₂O:26%, SiO₂: 21%, H₂O: 53% water 20 parts

One hardens at ambient temperature. The compressive strength at 7 daysis 40 MPa, and at 28 days is 105 MPa. The pH of the geopolymeric cementmeasured at equilibrium in a 10% solution is pH=12.14 after 7 days andpH=1 1.85 after 28 days.

It is interesting to compare the energy needs as well as the greenhousegas CO₂ emissions of traditional Portland cements vis a vis geopolymericcement according to the present invention:

type calcination crushing total Energy needs, MJ/tonne Portland cement3200 430 3430 geopolymeric 600 390 990 Greenhouse gas Emission, CO₂ intonne/tonne Portland cement 1.00 geopolymeric cement 0.15–0.20

The manufacture of geopolymeric cement by which the amorphous vitreousmatrix consists of a geopolymer compound of the Poly(sialate-disiloxo)type, with the approximate formula (Na, K, Ca)(—Si—O—Al—O—Si—O—Si—O), or(Na, K, Ca)-PSDS, requires 3.5 times less energy than that of Portlandcement; in addition, it emits 5 to 6 times less of the greenhouse gasCO₂. The industrial interest of the cements made according to thepresent invention is thus obvious.

Of course, various modifications can be made by the workers in the fieldto the geopolymeric binders or cements and the methods which have beenjust described simply as an example, whilst staying within the terms ofthe invention.

1. A geopolymeric binder or cement comprising an amorphous vitreousmatrix embedding mellilite particles, aluminosilicate particles andquartz particles, said particles having an average diameter lower than50 microns, wherein said amorphous vitreous matrix comprises aPoly(sialate-di siloxo) geopolymer compound, with the approximateformula (Na, K, Ca)(—Si—O—Al—O—Si—O—Si—O), or (Na, K, Ca)-PSDS.
 2. Thegeopolymeric binder or cement according to claim 1, wherein saidgeopolymer compound comprises a mixture of various varieties ofpolysialates in which the atomic ratio Si:Al varies between 2 and 5.5,the average of the values of the atomic ratio Si:Al being about 2.8 to 3other components of the said geopolymeric binder or cement, includingmellilite particles, the aluminosilicate particles and the quartzparticles, not entering into the calculation of this atomic ratio Si:Al.3. The geopolymeric binder or cement according to claim 1, wherein insaid amorphous vitreous matrix, the average of the values of the atomicratio Si:(Na, K) as measured with the electronic micro beam analysis isabout 6, varying from 3.096 to 9.681.
 4. The geopolymeric binder orcement according to claim 1, wherein in the said amorphous vitreousmatrix, the average of the values of the atomic ratio Si:Ca as measuredwith the electronic micro beam analysis is about 15 varying from 4.882to 41.267.
 5. The geopolymeric binder or cement according to claim 1,wherein the average grain size distribution of calcium mellilite glass,ranges between 15 microns and 25 microns, thus preventing thedissolution of these mellilite particles in the said amorphous vitreousmatrix.
 6. The geopolymeric binder or cement according to claim 1,wherein, during hardening at ambient temperature, calcium melliliteshows a reduction of 10 to 20% by weight of its content in CaO,accompanied simultaneously by an increase of 100 to 500% by weight ofits content in K₂O, the content of the other components like SiO₂, Al₂O₃and MgO, being unchanged.
 7. The geopolymeric binder or cement accordingto claim 1, wherein said aluminosilicate particles and said quartzparticles are found in a weathered granitic rock.
 8. The geopolymericbinder or cement according to claim 7), wherein said weathered graniticrock is a mining waste resulting from the extraction of coal.
 9. Thegeopolymeric cement according to claim 1, that during its manufactureproduces substantially no greenhouse gas, carbon dioxide, CO₂.
 10. Thegeopolymeric binder or cement according to claim 2, wherein in saidamorphous vitreous matrix, the average of the values of the atomic ratioSi(Na, K) as measured with the electronic micro beam analysis is about6, varying from 3.096 to 9.681.
 11. The geopolymeric binder or cementaccording to claim 2, wherein in the said amorphous vitreous matrix, theaverage of the values of the atomic ratio Si:Ca as measured with theelectronic micro beam analysis is about 15 varying from 4.882 to 41.267.12. The geopolymeric binder or cement according to claim 2, wherein theaverage grain size distribution of calcium mellilite glass, rangesbetween 15 microns and 25 microns, thus preventing the dissolution ofthese mellilite particles in the said amorphous vitreous matrix.
 13. Thegeopolymeric binder or cement according to claim 2, wherein, duringhardening at ambient temperature, calcium mellilite shows a reduction of10 to 20% by weight of its content in CaO, accompanied simultaneously byan increase of 100 to 500% by weight of its content in K₂O, the contentof the other components including SiO₂, AI₂O₃ and MgO, being unchanged.14. The geopolymeric binder or cement according to claim 2, wherein saidaluminosilicate particles and said quartz particles are found in aweathered granitic rock.
 15. The geopolymeric binder or cement accordingto claim 2, wherein said weathered granitic rock is a mining wasteresulting from the extraction of coal.
 16. The geopolymeric binder orcement according to claim 3, wherein in the said amorphous vitreousmatrix, the average of the values of the atomic ratio Si:Ca as measuredwith the electronic micro beam analysis is about 15 varying from 4.882to 41.267.
 17. The geopolymeric binder or cement according to claim 16,wherein the average grain size distribution of calcium mellilite glass,ranges between 15 microns and 25 microns, thus preventing thedissolution of these mellilite particles in the said amorphous vitreousmatrix.
 18. The geopolymeric binder or cement according to claim 17,wherein, during hardening at ambient temperature, calcium melliliteshows a reduction of 10 to 20% by weight of its content in CaO,accompanied simultaneously by an increase of 100 to 500% by weight ofits content in K₂O, the content of the other components including SiO₂,AI₂O₃ and MgO, being unchanged.
 19. The geopolymeric binder or cementaccording to claim 18, wherein said aluminosilicate particles and saidquartz particles are found in a weathered granitic rock.
 20. Thegeopolymeric binder or cement according to claim 19, wherein saidweathered granitic rock is a mining waste resulting from the extractionof coal.